NEET PG High-Yield: Dynamics of Transmission
Understanding how infectious agents spread is essential for disease control. This revolves around the Chain of Infection.
The Chain of Infection
| Link | Definition / Example |
|---|---|
| Reservoir | Habitat (Human, Animal, Environment). |
| Exit Portal | Respiratory, GI, skin, or transplacental. |
| Transmission | Direct (contact, droplet) vs. Indirect (vehicle, vector, airborne). |
| Entry Portal | Usually, the same as the exit portal (e.g., mouth, nose). |
| Susceptible Host | Individuals lacking immunity (age, nutrition, genetics). |
High-Yield NEET PG Pearls:
- Incubation Period: Time from infection to appearance of first symptoms.
- Serial Interval: Time between successive cases in a chain of transmission.
- Herd Immunity: The resistance of a group to invasion/spread of an infectious agent, based on a high proportion of immune individuals.
- Basic Reproduction Number ($R_0$): The average number of secondary cases produced by a single primary case in a completely susceptible population.